Surface Modification Of Mineral Particles Via Micro-nano High Internal Phase(HIP)emulsion

The clean processing of raw coal produces a large amount of high ash content,fine-grained slime.When the traditional collectors were used in the flotation processes for the above mentioned coal slime,the large consumption of reagents and low separation efficiency emerge as very challenging problems.The emulsification treatment of traditional collectors could effectively reduce the dosage of reagent.For example,oil-in-water emulsion collectors have been widely reported.In this paper,a novel collector of water-in-oil high internal phase(HIP)emulsion was prepared by emulsifying the traditional collector.Based on the analysis of its properties,the effects of the HIP recipe on its flocculating ability was studied,and the flocculating pattern as well as flotation kinetics under high-shear stirring were also discussed.The employment of HIP emulsion for floc-flotation process was optimized to achieve the best separation efficiency.By using microscope,conductivity meter and rotary rheometer etc.,the internal microstructure,stability and rheology of HIP emulsion were studied.The observation by microscope showed that the diameters of internal dispersed phase were in the range of 1～10 μm.The rheology test demonstrated that the HIP emulsion was non-Newtonian pseudo-plastic fluid.The stability and dispersion of HIP emulsion were studied by stirring HIP emulsion in water with high speed,the result of which showed that over 80% of internal salt solution phase would be released after 20 seconds stirring and subsequently transformed into an emulsion of homogeneity and flowability accompanied with original HIP emulsion fragments.Taking Jinda coal slime as the experimental coal sample(ash content on air-dried basis is ～52% and averaged particle size of d50 is ～8 μm),the recipe of HIP emulsions was optimized by evaluating its performance in the floc-separation process.The volume ratio of Span80 and kerosene,concentrations of Na Cl,Na2SO4 and KCl were considered.With the floc-separation performance and economy as the optimizing target,the HIP emulsion of 3:5 volume ratio of Span 80 and kerosene,0.3 mol/L sodium sulfate solution was identified.The stirring speed for slurry conditioning and flotation time were investigated on the HIP emulsion floc-floatation process.The results showed that a higher stirring speed could benefit the separation efficiency and a proper elongation of the flotation time could significantly improve the combustible recovery with a satisfying ash content of product.By laser particle size analyzer,the effects of stirring time on the variation of floc size using HIP emulsion and kerosene were studied,the results showed that the flocculating ability of HIP emulsion wasstronger than kerosene,and high shear pretreatment of about 20 s would lead to the highest recovery of combustibles with HIP emulsion.When the time of high shear pretreatment was longer than 20 s,the ash content of clean coal would be reduced with a high recovery of combustibles.Compared with kerosene,the HIP emulsion could save 90% of the amount of collector.The effect of HIP emulsion on the interfacial tension of slurry was studied and various flotation kinetic models were employed to predict the flotation behavior,the results showed that the HIP emulsion could reduce the interfacial tension of slurry and the first order matrix distribution kinetic model fitted best.